The sharing of mobile phones is an interesting phenomenon, and an example of market competition in action.
It also means phone usability in that market is important as people switch between different phones.
I have recently been in Colombia, South America where I spoke about usability for successful e-government at Andicom, Latin America's largest telecoms and technology conference organised by the country's IT research organisation CINTEL.
In the free time I had in Bogotá, I couldn't help but notice the many people on the street offering "llamadas 200 pesos / minuto" or calls on mobile phones for about £0.07 per minute.
It was clearly a thriving business in busy Bogotá, and many of these walking phone booths had three or more mobile phones in use at one time.
As shown in the photo below, they usually had the phones attached to themselves through small chains to help ensure their phone did not get carried away with the caller.
The practice was a good example of a competitive market in practice as one man shown was charging just 150 pesos per minute, undercutting his rivals by 25% and gaining a lot of business as a result.
He is also ready for a volatile market - he has a series of signs bound together so that he can quickly change the price should he see that other phone time sellers change their rates.
One of the interesting facts that I picked up while there was regarding the mobile phone penetration rate among Colombians, which was estimated to be about 75 to 80% based on the number of phones sold compared to the population.
Clearly practices such as the sharing of mobiles will call some of the data into question, and also remove some of the expectations that we might have about a very personal relationship with our phones for storing data, viewing favourite web pages, sending text messages etc.
Also with the sharing of mobile phones it means people will be using different models all of the time, so mobile phone usability will be important, although making a call should be the simplest of functions.
The practice shows a great deal of initiative in the bustling economy of Colombia, a country I would highly recommend for a visit - wonderfully friendly people, and interesting history.
Chris Rourke is the MD of User Vision .